Sliding skid rings of the type to which the present invention relate are required in the installation of pipes such as gas lines or waste water pipes into jacket pipes and to support them therein without metallic contact between the gas lines and jacket pipes. This type of installation for laying underground pipes has the advantages that it obviates the need for expensive excavation work. This type of installation is particularly advantages in situations where it is impossible or extremely labor intensive to excavate the area where the pipes are to be laid, such as when pipes are to be laid underneath the surface of a reinforced roadway. In these installations, vertical shafts are dug at the beginning and end of the segment and a bore hole is then made connecting the two shafts. The bore hole can be dug out by means of a compressed air tool, for example. A jacket pipe is then inserted into the bore hole so formed which functions to stabilize the bore hole and to hold the actual utility pipeline. The utility pipeline is pushed into the jacket pipe and to this end, is provided with sliding skid rings which attach to the external periphery of the utility pipeline at predetermined intervals such as every meter, for example.
Prior to the present invention, sliding skid rings typically consisted of a polymeric material such as polyethylene because it possessed the desired sliding properties and also was able to center the utility pipeline inside the jacket pipe. These materials also reliably prevent metallic contact between the jacket pipe and the utility pipeline which is important to ensure no corrosion phenomena will occur.
Presently, sliding skid rings of the type presently known are in the form of half-shells or quarter-segments which are then fastened together by high-grade threaded steel bolts. This assembly has certain disadvantages and drawbacks. For example, they tend to corrode over a period of time. Furthermore, the on-site installation of sliding skid rings is rather difficult because the production of screws/nut connections is relatively labor intensive. Furthermore, these screw/nut connections are rather difficult to connect speedily since the workmen are usually wearing cumbersome work gloves. In short, dealing with a relatively large number of small parts is rather tedious, time consuming and counter-productive.
Sliding skid rings which are equipped with solid plastic sliding skids are also known and typically are used for pipes with nominal diameters of more than 500 CMS. It has been known that these skid rings are also difficult to install since they require complicated pliers or clamping shoes for tightening. It has also been observed that the clamping action of these skid rings tend to diminish over a period of time and present the danger of the sliding skid ring coming loose.